Electric fluid heater



April 25, 1933. w, EVANS 1,906,145

ELECTRIC FLUID HEATER Filed Aug. 9, 1930 INVE TOP? 17- Z. vans BY v 2 ATTORNEYS Patented Apr. 25, 1933 PATENT OFFICE WILLIAM EVANS, or WASHINGTON, I IANA ELEcTRic FLUID HEATER Application and ugust a, 1980. Serial No. 474,176.

This invention relates to electrical heating apparatus and, among other objects, aims to provide an improved coil heater installation adapted to heatwater or generate steam very quickly and economically by using low volt age current so that the system is eminently a apted for household heating and other domestic or commercial uses.

Thisapplication involves important improvements on the apparatus shown in my copending application, Serial No. 47 4,17 5 filed August 9', 1930. I

In the accompanying drawing, I a Fig. 1 is a vertical sectional view of an installation embodying the invention; and I Figs. 2, 3, 4L and 5 are sectional views taken on the lines 2-2, 3-3, 4.-4 and 5.5 respectively in Fig. 1. I I

a .One of the reasons why the ordinary eleco tric heaters have not been practicable for use in heating systems resides in the fact that the heating elements consume too much-current and are not capable of heating water as rapid- I ly and economically as ordinary fuels. I The 5 capacity of an ordinary hot water tank is usually not less than eighteen gallonsand that of waterheating systems is usually con-, siderably more, depending upon the number and size of the radiators used. The ordinary heaters now. on the market cannot raise the temperature of such large quantities of water one hundred degrees in. less than an hour. Some of them require one minute per degree 1 rise. This invention provides highly 'im- 35 proved apparatus capable of heating arelatively large volumeof Water economically and raising the temperature from to degrees per minute. The invention also contemplates an arrangement whereby the apparatus can be used as an. instantaneous hot water heater for domestic or commercial use.

Referring particularly to the drawing, the apparatus there shown is similar in many respects to that in my aforesaid co-p ending application. The coil heater, hereinafter de: scribed in detail, is shown as being mounted in an insulated cylindricaljcasing l0 preferably made of non-conducting material and having'upper and lower end wallsll. "A

plurality of corrugated sheet metal resistance elements 12 are arranged in the casing around the heater elements or coils and connected at their opposite ends to pairs of bus bars 13. Current at low voltage is supplied to the resistance unit-s through annular conductors or bars 14 and conductors 15 which are connected to the .low side of a step-down transformer 16 adapted to receive current at any ordinary voltage, such as that employed in house installations. All of these features are shown in my co-pending application and require no furtherdescription.

In. this example, the heater comprises a plurality of coaxial tubular coils 17, 18 and 19 spaced from the corrugated resistance units and from each other. They are prefer ably connected in series by cross pipes having union'c'ouplings 20 so as to facilitate assembly andremoval for repairs. The tubes are preferably made of copper or some other metal having a high coeflicient of heat conductivity and the walls are as thin as a reasonable factor of safety will permit. A thickness of 3 2' of an inch has produced excellent results; In fact, an installation of this type will raise the temperature of eighteen gals lons of water one hundred degrees in less than five minutes.

Referring to Fig. 1, a supply pipe 21 from any suitable source is connected to supply Water or other fluid to the outside coil 17 and a force pump 22, preferably driven by a motor M, is employed to boost the pressure and increase the circulation through the coils. However, a valvedby-pass 23 is connected around the pump so that the system may be operated at the prevailing pressure in the water main or source of supply. The arrangement is such that water circulates through the coils, passing up through coil 17, down through coil 18 and up through coil 19 when three coils are used. The cold or returned Water supplied tothe heater absorbs heat from the walls of the tubular coils and the temperature rises until it is discharged through the outlet. More heat will be absorbedfor a given time as the circulation increases or speeds up. I

"As disclosed in my aforesaid application,

the heater is shown as having a discharge pipe 24 connected to the trunk line or conduit 25 of a radiator heating system, the return line or pipe 26 of which is connected to the heater inlet or supply pipe 21. A suitable check valve 27 opening downwardly, is arranged in the return line to prevent cold water from entering it. The water returned from the system is re-circulated through the heater. Further, manually operable valves 28 in the discharge and return lines and a valved by-pass 29 are preferably provided to enable the heating system to be cut off and the circulation to continue through the bypass to the return line and the coils. Also, a hot water service branch 30 is conveniently connected to the main discharge conduit so as to supply hot water for domestic or commercial use either when the heating system is in use or cut oil.

The system may be operated automatically so as to maintain a uniform temperature of the discharging water or fluid by means of a suitable thermostat 31 connected to the discharge pipe andcontrolling a switch (not insulated casing. It is absorbed by all of the tubular coils which present a very large heating surface in .a relatively small space. The casing walls are also heated to some extent by induced current, further increasing theefliciency. The apparatus is very compact and all of thelparts, including the separate coils, are easily removable for repairs or replacement. The resistance units will last almost indefinitely because they are not heated to extremely high temperatures. Moreover, installations of this type can easily be converted into steam or vapor generators for steam or vapor heating systems. Also, they may be utilized for heating air by circulating. air through the casing, as disclosed and claimed in my co-pending application, Serial No. 474,175 filed Aug. 9, 1930.

Obviously, thepresent invention is not restricted *to the particular embodiment therer of herein shown and described. Moreover,

it is not indispensable that all the features of the invention be used conjointly, since they may be employed advantageously in various combinations and sub-combinations.

lVhat I claim is 1. In a water heater installation of the character described, a casing; electrical heating means including a plurality of sheet metal resistance units within the casing ad- 5 jacent to the inner wall; and :a plurality of thin-walled, tubular coils coaxial with each other and connected in series adjacent to and surrounded by said heating means.

2. In a fluid heater installation of the character described, a casing; a substantially cylindrical series of electrical heater elements Within the casing; a plurality of coaxial coils within the casin adjacent to and surrounded by the heating elements; conduits connecting said coils in series; supply and discharge pipes connected'to'the coils; and a pump to circulate fluid through the coils.

3. In a-fluid heater, asubstantially cylindrical casing having end closures; a substantially cylindrical series of corrugated sheet metal resistanceunits in the casing; tubular coils arranged adjacent to and surrounded bysaid resistance units; and conduitsconnected to the coils and arranged to circulate the fluidthrough a radiator heating system.

4. In a fluid heater, a substantiallycylindrical casing having end closures; a series of corrugated sheet metal resistance units in the casing; a plurality of coaxial tubular coils arranged adjacent to and surrounded by said resistance units; means removably connecting said coils in series; a fluid suply pipe connected to the coils; means to estab ish continuous circulation through the coils; and a pump in the supply pipe to circulate the water through the coils.

5. In a fluidheater, a substantially cylin drical casing having end closures; a cylindrica-l-sha-ped series of corrugated sheetmetal resistance units in the casing; tubular coils arranged adjacent to and enclosed bysaid resistance units; means removably connecting said coils in series; a fluid supply pipe connected tothe coils; means to establish continuous circulation through the coils; a-pump in the supply pipe to circulate the Water through the coils; a discharge pipe connected to one of the coils.;.and aradiator returnpipe connected to the inlet supply pipe.

6. In an electric fluid heater of the class described, a substantially cylindrical casing composed of nonconducting material; resistance heating units arranged in substantially cylindrical formation within the easing; a plurality of coaxial coils in the casing enclosed by the heating units composed of thin-walled tubing having a high coefficient ofheat conductivity; and inlet and discharge pipes connected to said coils.

7. In a water heater of the class described, a vertical, cylindrical casing; electric heater elements arranged in cylindrical formation and spaced from the inner wall of the casing; a tubular coil adjacent to the heater elements; a Water supply pipe connected to the lower end of the coil; a discharge pipe for the coil adapted to be connected to the trunk line of a radiator heating system; a return pipe for the heating system connected to the water supply pipe; a hot water service pipe connected to the discharge pipe; valves in the discharge and return pipes; and a valved by-pass connecting said pipes, whereby the installation may be utilized as an instantaneous water heater.

8. An electric fluid heater of the character described, comprising an insulating casing; electric heater elements in the casing; a stepdown transformer connected to deliver current at low voltage to the heater elements; tubular coils in the casing adjacent to the heater elements; means connecting the coils in series water inlet and discharge pipes connected to the coils; means for re-circulating heated Water through the coils; and thermostatic control means connected to the discharge pipe.

9. A water heater for hot Water heating systems comprising, in combination, a plurality of coaxial, tubular coils connected in series; corrugated, sheet metal resistance units spaced from and surrounding the coils; and means to supply current at low voltage to said resistance units.

In testimony that I claim the foregoing as my own, I have hereto affixed my si nature.

W. L. E ANS. 

